This invention relates to a location system which can be used, for example, to locate personnel or vehicles in an underground mine.
Various location systems are known which use passive transponders or low-powered active devices with miniature internal batteries. Such devices have very short operating ranges, of the order of 1 m or less. This requires identification or location systems using such devices to rely on movement restricting systems such as turnstiles or automatic doors to channel personnel issued with the devices past an identification station.
In certain environments, such as underground mines, such impediments to free movement may be impractical or may be unacceptable for safety reasons. In addition, it may desirable to implement a more flexible location system, which is difficult if identification stations include movement restricting structures such as those referred to above.